Table salt (sodium chloride) is an essential nutrient for human beings. For example, table salt plays an important role in functions as exemplified by control of bodily internal water content, pH, and osmotic pressure, digestion of foods, absorption of nutrients, neurotransmission, muscle activity, or the like. Table salt has a wide variety of roles in foodstuffs. Examples of such roles include enhancement of delicious taste or savoriness, imparting texture, retention of color, or the like. The effect on flavor of foodstuffs is great, and the addition of table salt enhances sweetness and delicious taste, and decreases unpleasant bitterness. However, excessive intake of table salt is thought to increase the risk of occurrence of lifestyle-related diseases such as high blood pressure, kidney disease, heart disease, cancer, or the like. From the standpoint of prevention of increased risk of lifestyle-related diseases due to excessive intake of table salt, in the “Japanese Dietary Intake Standard (2010 edition)”, the Ministry of Health, Labor and Welfare sets a target intake of table salt for an adult of less than 9.0 g/day for men and less than 7.5 g/day for women. The amount of table salt intake by adults according to the 2009 national nutrition and health survey was 11.6 g/day for men and 9.9 g/day for women, and this intake has not been reduced to the target values, which continue to be lowered year by year. The WHO and International Society of Hypertension guidelines recommend less that 6.0 g/day table salt intake.
Simply decreasing the utilized amount of table salt in food or drink flavoring and processing has been considered as a method to decrease the intake of table salt. However, as mentioned above, table salt plays an important role in determination of quality of foodstuffs. Thus, savoriness is harmed and flavor is lost in a food or drink in which the utilized amount of table salt is simply decreased during flavoring and processing. For the development of low-salt foodstuffs, it is most important to attain both robust saltiness and delicious flavor even though table salt content has been reduced. There is a strong need to develop technology to realize such attainment.
By addition of a non-table salt substance that has saltiness, it is possible to make up for the low saltiness that occurs when table salt is decreased. Known examples of substances that have saltiness include potassium salts such as potassium chloride or the like, magnesium salts such as magnesium chloride or the like, calcium salts such as calcium chloride or the like, and ammonium salts such as ammonium chloride or the like. In comparison to sodium chloride, these substances are characterized by having weak saltiness and having unpleasant bitterness, astringent taste, harsh taste, bitter taste, or the like. Moreover, although considerable research has been performed at the molecular level relating to taste sensing, the detailed sensing mechanisms for the expression of such saltiness or bitterness, astringent taste, harsh taste, bitter taste, or the like by such salt substitute substances have not been resolved. Known examples of technologies for using such salt substitute substances, decreasing table salt, and suppressing non-salty unpleasant tastes include: a flavoring composition that mixes potassium chloride, ammonium chloride, calcium lactate, sodium L-aspartate, L-glutamic acid salts, and/or nucleic acid type flavoring substances at specific ratios (Patent Document 1); a method for suppression of the bitterness of potassium chloride by combination with a calcium salt or magnesium salt of an organic acid (Patent Document 2); a taste improver of a potassium chloride-containing food or drink that uses a basic amino acid (such as histidine, arginine, and lysine) and/or basic peptide (such as anserine, carnosine, and balenine) as an active ingredient (Patent Document 3); a taste improver for potassium salts that contains poly-γ-glutamic acid or a salt thereof (Patent Document 4); a mineral taste improver that includes a sugar phosphate ester (Patent Document 5); a method for removal of bitterness of potassium chloride by combined use with carrageenan (Patent Document 6); a table salt substitute that blends with potassium chloride at specific ratios sodium gluconate and/or potassium gluconate, and whey mineral (Patent Document 7); a powder flavoring that contains at specific ratios sodium, a non-sodium alkali metal or an alkaline earth metal, and a flavonoid (Patent Document 8); a method of use of trehalose for suppression of bitterness and/or metallic flavor of potassium chloride (Patent Document 9); a taste improver for potassium salt or a potassium salt-containing food or drink that includes quinic acid or quinic acid-containing composition, spilanthol or spilanthol-containing plant extract or refined plant oil, and Allium plant extract (Patent Document 10); or the like. However, it has not been possible to sufficiently suppress unpleasant non-salty taste, and due to unpleasant flavor or the like derived from the taste improvement materials, technology for meeting the needs of consumers has not been achieved.
On the other hand, substances other than potassium salts, magnesium salts, calcium salts, and ammonium salts that have unpleasant bitterness, astringent taste, harsh taste, bitter taste, or the like are exemplified by: alkaloids such as quinine and caffeine; polyphenols such as catechin and tannin; protein hydrolyzation products such as peptides and amino acids; and sweeteners such as aspartame, sucralose, acesulfame potassium, and neotame. As a technology for suppression of such unpleasant flavors, the following are disclosed: the suppression of bitterness of grapefruit juice, coffee, and quinine hydrochloride by use of a bitterness suppression agent that contains phosphatidic acid and phosphatidyl inositol (Patent Document 11); a bitterness-reduction agent containing an acidic phospholipid or its lyso form as a bitterness reduction component for the reduction of bitterness of quinine hydrochloride and quinine sulfate (Patent Document 12); a composition for foodstuffs that includes a bitter-tasting substance selected from the group consisting of bitter amino acids and bitter peptides, and a phospholipid selected from the group consisting of acidic phospholipids and lyso forms thereof (Patent Document 13); a highly sweet sweetening agent taste improver that includes solvent extract of roasted coffee (Patent Document 14); a highly sweet sweetener taste improver that includes vicenin-2 (Patent Document 15); a drink that has taste improved by a high sweetness sweetening agent that includes vegetable juice (tomato, carrot, or celery) and alcohol (Patent Document 16); a high sweetness sweetening agent taste improver that includes ginger extract and at least one oil selected from the group consisting of caraway essential oil, peppermint tail essential oil, cardamom essential oil, nutmeg extract, and hop essential oil (Patent Document 17); a bitterness suppression agent for quinine sulfate that has as an active ingredient a mammal-derived collagen peptide that has an average molecular weight of 500 to 4,500 (Patent Document 18); a method for lowering of bitterness of a turmeric extract or basidiomycetes extract that uses a neutral phospholipid derived from a natural substance (Patent Document 19). However, the technologies described in the aforementioned Patent Documents 11 to 19 are not developed from the standpoint of improvement of the taste of potassium salts, magnesium salts, calcium salts, and ammonium salts. Due to differences in affinity toward solvents, it is thought that the mechanism for sensing unpleasant bitterness, astringent taste, harsh taste, bitter taste, or the like is different.